In Science Today we did an experiment. We put an empty can over a bunson burner until it was heated and then with tongs quickly put it (inverted) into cold water, it immidietley collapsed! Can you please please explain why?

basically, it can’t handle the pressure change, because cold water is at a higher pressure than normal air, and therefore collapses when submerged into cold water. also the temperature change is unbearable and creates stress in the can

Did you add a little bit of water perhaps to the can before heating it? My guess would be that the water molecules when heated would saturate the air and basically push it out. When you put the can in the cold water, these gas vapors of water that were heated condense and as a result, the outward pressure drops, and the volume does the same.

The outside pressure is what would crush the can because once the can is cooled in water, the outside pressure will be vastly greater.References :

basically, it can’t handle the pressure change, because cold water is at a higher pressure than normal air, and therefore collapses when submerged into cold water. also the temperature change is unbearable and creates stress in the canReferences :
chemistry teacher

If the can was filled with steam or air that contains "a lot" of steam, then, when the steam condenses back into liquid water, there is a large decrease in volume. If the air can not rush in to replace the "missing" volume, atmospheric pressure will crush the can.

In your case, your can must have been open to the air otherwise it would have blown up when heated. If the hole in the can was very small, the liquid water would not have been able to flow into the can fast enough to replace the "missing" air volume so atmospheric pressure would have crushed it.

You can check out youtube video of this being done with a steel 55 gallon drum, it collapses with significant effect.References :

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